1. Field of the Invention
The present invention is generally directed to a foldable bifocal intraocular lens during insertion in the eye may be made smaller than the width when implanted, thereby requiring a smaller incision in the cornea than is now the case for implantation, and more particularly to an improved foldable lens having a resilient means which, once inserted and released, returns the lens to an operational configuration without further manipulation.
2. Description of the Prior Art
Many different types of synthetic intraocular lens structures have been developed to replace the natural lens of the human eye after lens removal during cataract surgery. In such operations, an opening or incision is made in the cornea and in the anterior surface of the capsular bag. The damaged lens tissue is removed by means of a vacuum tool resulting in loss of vision to the affected patient. In order to restore normal or correctable vision, a variety of lens structures have been developed which are designed to be affixed in the intraocular space of the eye. Such structures commonly comprise a centrally positioned lens and a plurality of appendages attached to the lens which function to position and secure the lens in front of or just behind the pupil.
The artificial lens is formed from an optically clear substance and shaped so as to focus impinging light onto the retina of the eye. Such lenses are commonly optically formed to be plano-convex, convex-plano, meniscus or bi-convex. The appendages attached to the lens typically comprise flexible legs of resilient plastic or metal fibers which are designed to make contact with appropriate structure in the interior of the eye.
One commonly employed type of intraocular lens structure is designed to position the lens in the anterior chamber of the eye just in front of the pupil. A structure of this type is disclosed, for example, by Kelman (U.S. Pat. No. 4,451,938). Another commonly employed type of intraocular lens structure is designed to position the lens in the posterior chamber of the eye just in back of the pupil. Devices of this type are disclosed by Faulkner (U.S. Pat. No. 4,366,582) and Shearing (U.S. Pat. No. 4,159,546). Streck (U.S. Pat. No. 4,361,913) discloses a lens which is indicated for possible use in either the anterior or posterior chambers.
Each of the structures mentioned above, except that of Kelman, is comprised of a single element lens with a plurality of haptics or positioned-fixation members attached to the lens. The lenses ordinarily have a circular perimeter. Thus, the incision in the cornea of the eye must be at least as long as the diameter of the lens. It is clear that the longer the incision, the greater will be the trauma to the eye and the longer will be the recovery time. Furthermore, since cataract surgery is usually performed on older patients, the general health of the patient may make it exceedingly important to keep the incision as short as possible. With this in mind, Kelman discloses in U.S. Pat. No. 4,451,938 an intraocular lens which is separable into two body portions. Each body portion is inserted separately through the cornea and the lens is then reassembled inside the eye during emplacement. Such lens structure certainly leads to the necessity for a shorter incision in the cornea than would otherwise be the case. The Kelman device, however, leads to delicate manipulation of the parts within the eye in order to reassemble the intraocular lens.
European Patent Application No. 83303414.3 by Kelman discloses an intraocular lens which may be inserted into an eye through a smaller incision. The optic is deformable by either folding a flexible optic lens body or by hinging a lens body. When hinging action is utilized, it is necessary for the hinges to be manually returned to their operational configuration after the lens has been inserted into the eye. The present invention addresses the problem of keeping the incision as short as possible in another way and also provides for a bifocal intraocular lens.